Hydrogen evolution from cathodically charged Ti₃Al-based titanium aluminum alloy

A single-phase Ti₃Al-based titanium aluminum alloy, Ti-25Al, was cathodically charged with hydrogen in a 5% H₂SO₄ aqueous solution for charging times up to 43.2 ks, and the formation and dissociation of a hydride, hydrogen evolution behavior and total hydrogen uptake were investigated by means of X-ray diffractometry and thermal desorption spectroscopy (TDS). After cathodic hydrogen charging, hydrogen concentrated mainly at the surface of the sample as a hydride phase, whose crystal structure probably is of a hexagonal type with the lattice parameters of a = 0.60 nm, c = 0.47 nm. Hydrogen also induced cracks and pits at grain boundaries or within grains. Three kinds of TDS peak, for which one corresponded to the hydride dissociation and the others presumably corresponded to trapping of hydrogen, could be found after longer hydrogen charging. The apparent hydrogen uptake in the Ti-25Al alloy increased with increasing charging time and the uptake level after charging for 43.2 ks was estimated to be about 700 wppm.